High Ash Content in Cat Food & Renal Failure in Cats

Phosphorous matters for a cat with chronic kidney disease.
i David De Lossy/Valueline/Getty Images

Veterinary science has made great strides. Over the last couple of decades, researchers have learned that high "ash content" in catfood isn't as harmful as once believed. If Bella's in renal failure, ash content is one part of her diet you don't have to fret.

Ash Content in Cat Food

If Bella's been dining on kibble, one of the ingredients listed on the label is the ash content. Don't worry -- no one's been snuffing out cigarettes in her food. Ash, mostly minerals, is a score of the inorganic content that remains after a sample of Bella's food has been incinerated. In the 1980s, vets commoly recommended a low-ash diet for cats suffering from urinary tract problems. The idea was that struvite, a type of bladder stone, was caused by diets with high ash content. As more research was conducted, it became clear that magnesium level is of greater concern than ash content.

Chronic Renal Failure

Though they're little organs, kidneys have a big job to do; along with helping to regulate Bella's blood pressure and maintain her hydration level, they remove toxic substances from her body. Waste products such as phosphorus, nitrogen and creatinine, are filtered from her blood by her kidneys and excreted in her urine. Kidneys are able to compensate for their own deterioration, so kidney disease is usually advanced by the time it's detected. Normally, renal failure in cats isn't detected until there's only about a third of healthy kidney function left. There are a few known causes of kidney disease, including infection, cancer and ingesting toxins such as antifreeze. Though diet doesn't cause kidney disease, it can contribute to the kidneys' deterioration.

Ash Content and Kidney Failure

Ash content in Bella's food doesn't have much to do with what's going on in her kidneys. A high level of ash isn't going to make her sicker, nor did it cause her renal failure. The only known connection between ash content and renal failure is the presence of water or lack of it. Dry food, which has ash, has very low water content compared with that of canned food. If Bella has kidney issues, water intake is crucial for her; she'll get more water from canned food. The Feline Nutrition Education Society notes that the chronic mild dehydration cats experience from dry food diets can stress the kidneys, ultimately impacting kidney function. As well, the low magnesium content in foods formulated for urinary health may negatively impact the kidneys over time, but evidence isn't conclusive on that.

Diet and Kidney Failure

As kidneys fail, it becomes harder for them to process toxins. Debate exists over the role of protein in the diet for a cat in renal failure. Some vets advocate a diet low in protein, on the premise many of the toxins present in the kidneys are from the breakdown of proteins. Other vets point out the difference between protein and high quality protein, which is protein that meets Bella's nutritional needs but needs as little breaking down as possible. Despite the disagreement over protein, the role of phosphorous isn't under debate. A cat in kidney failure isn't able to process excess phosphorous, which can hasten the deterioration of her kidneys, as well as cause nausea, loss of appetite, weight loss, weakness and loss of coordination. A cat in chronic renal failure requires a diet low in phosphorous.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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